


the things we don't say

by grundlemuncher



Series: the path of least resistance [1]
Category: Undertale (Video Game)
Genre: Ecto-Penis (Undertale), Ecto-Vagina (Undertale), Edging, Fontcest, M/M, Oral, Sibling Incest, Unrequited Love
Language: English
Status: Completed
Published: 2016-12-25
Updated: 2016-12-25
Packaged: 2018-09-12 03:37:22
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,426
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9053641
Author URL: https://archiveofourown.org/users/grundlemuncher/pseuds/grundlemuncher
Summary: in hindsight, platonic brother fucking could only go on so longin which papyrus gets feelings





	

**Author's Note:**

  * For [sin_bin](https://archiveofourown.org/users/sin_bin/gifts).



You see, there's this thing they do.

It’s not everyday - it’s not even on a routine, when they do. Once a month, maybe, or maybe not at all for many months and then a few times in a week. It’s just another part of them - like how Papyrus loves puzzles but will indulge in a well-crafted pun from time to time, or how Sans can be really brilliant when he tries, though he’d rather be sleeping.

It’s just another aspect of the goofy skeleton brothers who dick around in the snow hunting for humans all day, to the varied despair and delight of Snowdin’s long-time residents. They make snowmen, and keep the forest teens out of trouble, and sneak food to the royal dogs, and tease each other mercilessly. 

And also, though the public doesn’t know this - they sometimes get each other off.

It’s not love-making. It’s like… bros with benefits, (bros with bonefits, sans jokes) kind of. Even that feels not quite right. There’s not a word for it - it just sort of happened, once, and then again. A slip-shod sex ed coupled with a birds-and-the-bees talk that went sideways, and, well. Sans always called it experimenting, to himself. Nothing permanent, nothing wrong. So long as he kept telling himself that.

Of course they both know not to get caught. It’s still _not-okay_ , but they’ve never really both been _okay_ , right? So as long as they keep walking this line of communication, where you talk just enough to make sure you’re not hurting, but not so much that this _experiment_ suddenly becomes _you’re fucking your brother_ , then. 

As long as it feels good, then.

As long as it makes Papyrus happy, then.

Then Sans hardly feels any shame at all when he starts his day with a seemingly accidental brush of his brother’s lower spine as they pass each other in the kitchen. Papyrus yelps, blushing, and Sans feigns innocence, hands already deep into his pockets.

There’s no shame at all when he lets himself be caught, unsubtly leering at his brother’s ass as he rights himself after mending a tripped breaker in the snow. Papyrus shoots him a warning look that Sans returns with a bright grin, and if Papyrus’ cheekbones glow before he looks away, Sans pretends not to notice.

It goes on like this all day. Standing too close when they’re alone in the forest, letting his gaze roam over his brother’s trembling bones. At one point Papyrus is certain Sans is just going to fuck him at his sentry station, having been backed into the counter, pelvis pressed against him. Sans rolls his thumbs over the tips of Papyrus’ hips, just peeking out from his shorts, until he’s panting and straining- and then blinks away with a wink. Papyrus has to bite down on his fist to keep from screeching.

It goes like this all day. So when Papyrus stomps home, ignoring the slurry of snow he tracks in the door, Sans is confident that Papyrus is dripping. 

His brother has never been one for wasting magic, and so this prolonged hold on his ectovagina has left him sweating and practically panting when Sans lazily stands from the couch and comes on to him again.

Papyrus glares. “ARE YOU MAKING GOOD ON THIS OR NOT?”

He is.

Papyrus is overly sensitive, dissolving into shivers and whines at the first quick brush of Sans’ hand across his clothed slit.

“alright?” Sans teases, voice lilting, but it fades at Papyrus’ broken face.

“PLEASE,” Papyrus begs, clinging to his hips hard enough to hurt. He nuzzles into into his brother’ neck breathing hard, like it’s the only place he can get oxygen from. “PLEASE, SANS.”

They’ve got this unspoken rule. There’s no names when they do this - not ‘bro’ or ‘BROTHER’ or ‘papyrus,’ and definitely not ‘SANS.’ It makes it too real, who they’re touching, what they’re doing. Like the first time they had sex face to face, chests pressed together, ribs interlocked. Papyrus had cried after, and Sans had sat there feeling vaguely nauseous as he rubbed his brother’s back, not making eye contact.

Papyrus, especially, doesn’t do much talking when it comes to their excursions, so Sans gets down to business, concerned he’s pushed his brother too far. Papyrus is all but puddy in his hands as he pushes him onto the couch and pulls down his shorts. He presses a quick kiss to Papyrus’ femur in silent apology before burying his face in his pussy.

Unsurprisingly, it takes only a few hard licks, followed by an added finger to Papyrus’ soaking hole as he suckles at his clit, before Sans watches from between his legs (the best angle he can imagine) as Papyrus cums embarrassingly fast.

The taller skeleton falls back against the couch with a huff, long limbs going loose, release reached without too much satisfaction. When Sans leans forward to kiss at his lower spine, he meets Papyrus’ tired frown.

“I DON’T THINK I LIKED THIS EDGING THING.” He grumps, gently pushing Sans’ skull away so he’s forced to meet his gaze. Sans smiles sadly before standing, climbing onto the couch to wrap his brother up in a bony embrace.

“my bad, bro.” Sans murmurs as Papyrus reluctantly relaxes against him, skull to skull. He rubs his teeth sweetly against Papyrus’ collarbone, leaning lower to graze against his higher ribs.

“can i make it up to you?”

He feels Papyrus’ apprehension more than he hears it, a full body shudder of pleasure dissolving into nervous rattling. “I DON’T… I DON’T KNOW IF I CAN GO AGAIN.”

“wanna find out?”

Papyrus glances at him, unsure but trusting, and Sans continues. “it could be like a puzzle.”

“MORE LIKE SCIENCE.” Papyrus replies, sighing, knocking his skull against Sans’ and making him laugh.

“OKAY.” Papyrus finishes with a quick, ticklish kiss to his crown. Sans pounces on the opportunity, his own erection straining at his sweatpants. He gently rearranges his brother, back pressed down onto the couch. The expectant look Papyrus gives him makes him shiver.

“say the word and i’ll stop.” Sans murmurs, hiking up his brother’s shirt as he kisses from rib to rib.

“WHAT’S THE WORD?” Papyrus’ hands have come up behind his back, fisting about his smaller spine. Sans jerks at the touch, thought momentarily lost.

“uh… it’s stop.”

“PRACTICAL.”

Papyrus looks away as Sans crams his sweatpants down past his knees, freeing his thick cock.

Sans gets caught up in kissing at every bit of Papyrus he can reach (an apology only he understands for an act they shouldn’t ever be doing). His brother sighs, and his lifts his own legs to let them drape over Sans’ shoulders. That gets his attention.

“FORGET WHAT YOU WERE DOING?” Papyrus asks, brow bone crooked.

“got a little sidetracked.” Sans replies, quickly dragging one hand down Papyrus’ ribcage, making him laugh.

“STOP, STOP,” he giggles, squirming away from his ticklish hands, helpless.

“i thought you said to start?”

“SANS!!”

“well make up your mind, bro.”

Sans is jolted from his reverie as Papyrus groans and pulls his hips forward, Sans’ cock brushing his soaked cunt. He looks up at him, teeth grit tight, something dark and altogether too-warm in his black gaze.

Sans is breathless atop his brother.

“ok.”

Sans slides into Papyrus’ cunt with ease, watching as each inch of himself sinks into his brother’s wet heat. Papyrus chokes on a moan, something that might have been “SANS,” if that had been allowed, breaking into breathless gasps as he’s filled, deeper and deeper.

Sans’ attempts to stay quiet die quickly. “god,” he curses, thrusting tentatively further into his brother. His grip comes up about the femurs pressed against him and he spreads them wide - Papyrus cries out - hilting himself impossibly deeper.

His hips are already rolling in circles, desperate for more. Still, Sans leans down, pressing as close to his brother as possible. “you okay?”

“YES,” Papyrus whines, a tone somewhere between his usual annoyance and hot arousal that makes Sans’ soul clench.

That’s all Sans needs. Renewing his grip on his brother’s femurs, Sans thrusts into him hard, setting a pace that surprises even himself. The edging might have had an effect on his lazybones, too. Papyrus would comment on it if he had the capacity for words.

His large hands fist about Sans’ shoulders, fit to break, as Sans rocks into him over and over. He’s incredibly swollen and sensitive, having never conjured his genitals for this length of time, and Papyrus can feel every slow drag of his brother’s thick cock as it hilts within him.

It’s entirely overwhelming.

Sans has never heard Papyrus make sounds like this before. His low voice is wrecked, cracking and wheezing as he fights to catch his breath. It’s a little scary, and stupidly arousing - so Sans plows on.

Papyrus switches from throwing his skull back in ecstasy and burying it in Sans’ neck, too eager and needy for closeness. In hindsight, he should’ve seen the signs. At the moment, Sans can only think about how good Papyrus feels about his cock, clenching with each thrust as though he can’t bare to let him go.

Sans can feels Papyrus getting close, walls fluttering about his cock as his brother grows frantic, gasping about broken syllables, phalanges scratching down the back of his ribcage in an earnest effort to warn him. There’s no need - the scrape of those long fingers and something that sounds suspiciously like his name sends Sans over the edge. With a grunt he cums hard into his brother, cramming himself in as far as he’ll go as Papyrus clenches up around him in an unconscious effort to pull him deeper.

Sans is so lost in his own throes he almost doesn’t hear his brother’s.

“SANS, I LOVE YOU- _ILOVEYOU ILOVEYOU-_ “

His soul stutter-stops in his chest, rising and falling above his brother’s, gasping for air that suddenly seems too cold.

Papyrus’ arms have fallen lax about him, loose and warm. He can feel a single, shaky thumb rubbing absently at the base of his spine.

Sans lets himself lay spent, skull buried in his brother’s sternum, for another over-long moment (coward). Then he raises his head.

Papyrus is looking down at him with heavy, tired eye sockets. His teeth are still parted, panting lightly for breath, as though the words that just burst from them have left him opened and empty. Sans feels all at once very small in his brother’s embrace.

“uh.” He says, intelligently.

There’s a burst of warm breath across his forehead as Papyrus half-laughs, half-sobs, cutting himself off with an audible click as he slams his teeth shut and turns his head to the side. His ribcage turns shaky beneath Sans, trembling with muted cries, and it’s all Sans can do to raise up on his arms with frantic urgency as he spies tears pooling in the corners of his brother’s eye sockets.

“hey- hey! it’s okay,” Sans says, flustered and terrified, reaching up to wipe at his brother’s cheeks as a few tears roll free. “it’s alright. heat of the moment, yeah? forget about it.”

He cups Papyrus’ face to turn it towards him, and flashes his most winning, pacifying smile. Papyrus does not return it.

“…I MEANT IT.”

Oh.

You see, there’s this thing they do. No one else knows about it, and they certainly don’t talk about it. It’s just blowing off steam, platonic if awful, temporary if so, so good. Intimate, yes, but not- not this, this, this-

This was messed up from the beginning, but Sans could never say no to Papyrus, and Papyrus rarely thought to ask Sans what exactly it was he wanted. It was casual, though. Once a month, maybe, they’d blow off some steam with the person they trusted most in the world, and then they’d separate and clean up and sleep it off, and the next day they’d just be brothers again.

This wasn’t brothers.

This wasn’t platonic, anymore.

His brother doesn’t just love him. He’s _in_ love with him.

Sans suddenly feels as if he’s done something unforgivable.

“IT’S OKAY.”

Papyrus drags him back to the present, this awful, terrible _now_ , with two words and a watery smile.

He sniffs, unconscious, before rubbing his hands hard over his eye sockets. He looks every bit the word fragile, and yet, Sans is stunned by the words coming out of his mouth.

“YOU DON’T HAVE TO LOVE ME BACK.” Papyrus says, with the forced casualness of a man whose met rejection head on a thousand times. Someone who had long planned for this reaction. He’s gently pulling away from his brother already - just walk it off, champ.

“papyrus-“ Sans starts, and stops, having never planned on finishing. His brother is still smiling as he gently lifts Sans by the hips. He slips out of his brother with a slick pop, spilling cum from Papyrus’ over-full cunt.

Papyrus presses his forehead lightly to Sans’, just once, like he might be kissing him goodnight or comforting him after a bad dream. When his dark eye sockets open again, so close Sans could fall into them, the moment passes. Ends.

Papyrus sets Sans down, half-naked, on the couch. He untangles and extricates his own long limbs in a flash, standing and redressing in a single movement. Papyrus looks so _tall_ , Sans thinks, himself already sinking lower into the couch, as though he could disappear (he won’t, though. he couldn’t ever leave his brother, even after this).

“SO.” Papyrus chirps, cheery, overcompensating. He doesn’t look at Sans, but he can still see the strained edge of a too-large smile. “HAVE YOU EATEN? I’M STARVING.”

And then he vanishes into the kitchen with four quick steps, leaving Sans bare-boned and hollowed out on the couch.

The too-familiar clang of cutlery from Papyrus’ overenthusiastic cooking sets Sans in motion once more. He doesn’t remember getting to his feet, or pulling his damp shorts back up over his hips. There’s cum - orange and blue, too bright and viscous and _alive_ \- drying on the couch, so he finds a washcloth from the bathroom and cleans it up. Washes his hands (Papyrus hates when he comes to the dinner table without doing so). Wanders into the kitchen half on habit and half- half-

Papyrus stands at the stove, whistling something indiscernible.

Slippers shuffling, Sans comes up behind and wraps his arms about his brother’s middle. Buries his face into the firmness of his spine. Smells like spaghetti.

“i’m sorry,” he says.

“FOR WHAT?”

**Author's Note:**

> happy candlenights my dudes! i haven't written in ages so, sorry if this reads weird. thank you for the prompt sin_bin you wonderful motherfucker, it got my gay ass back in the game!


End file.
